c4f2d992 |
1 | /* -*-c-*- |
2 | * |
3 | * $Id: idea.c,v 1.1 1997/07/21 13:47:49 mdw Exp $ |
4 | * |
5 | * IDEA encryption routines |
6 | * Based on Straylight ARM assembler routines |
7 | * |
8 | * (c) 1996, 1997 Mark Wooding |
9 | */ |
10 | |
11 | /*----- Licencing notice --------------------------------------------------* |
12 | * |
13 | * This file is part of `become' |
14 | * |
15 | * `Become' is free software; you can redistribute it and/or modify |
16 | * it under the terms of the GNU General Public License as published by |
17 | * the Free Software Foundation; either version 2 of the License, or |
18 | * (at your option) any later version. |
19 | * |
20 | * `Become' is distributed in the hope that it will be useful, |
21 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
23 | * GNU General Public License for more details. |
24 | * |
25 | * You should have received a copy of the GNU General Public License |
26 | * along with `become'; if not, write to the Free Software |
27 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: idea.c,v $ |
33 | * Revision 1.1 1997/07/21 13:47:49 mdw |
34 | * Initial revision |
35 | * |
36 | */ |
37 | |
38 | /*----- Notes -------------------------------------------------------------* |
39 | * |
40 | * This code is optimised for 32-bit processors with reasonable numbers of |
41 | * registers. Hopefully it should still work on a Spectrum, although rather |
42 | * slowly. I do assume two's complement arithmetic. |
43 | * |
44 | * Since this is actually /decompiled/, by hand, from some existing assembler |
45 | * code, you can expect some parts to be a little strange. |
46 | */ |
47 | |
48 | /*----- Header files ------------------------------------------------------*/ |
49 | |
50 | #include <stdio.h> |
51 | |
52 | #include "config.h" |
53 | #include "idea.h" |
54 | #include "utils.h" |
55 | |
56 | /*----- Low-level support functions ---------------------------------------*/ |
57 | |
58 | /* --- @idea__inv@ --- * |
59 | * |
60 | * Arguments: @int n@ = number to invert |
61 | * |
62 | * Returns: Multiplicative inverse of n, mod 2^{16} + 1 |
63 | */ |
64 | |
65 | static int idea__inv(int n) |
66 | { |
67 | long m, a, b, q, r, t; |
68 | |
69 | /* --- Check the easy case --- */ |
70 | |
71 | if (!n) |
72 | return (0); |
73 | |
74 | /* --- Start off the loop --- */ |
75 | |
76 | m = 0x10001L; |
77 | a = 1; |
78 | b = 0; |
79 | for (;;) { |
80 | q = m / n, r = m % n; |
81 | if (!r) |
82 | break; |
83 | m = n, n = r; |
84 | t = a, a = b - q * a, b = t; |
85 | } |
86 | |
87 | /* --- Get return value in range --- */ |
88 | |
89 | if (a < 0) |
90 | a += 1; |
91 | return ((int) a & 0xFFFF); |
92 | } |
93 | |
94 | /* --- @_mul@ --- * |
95 | * |
96 | * An evil macro to do multiplication. Satan lives here. |
97 | */ |
98 | |
99 | #define _mul(x, y) \ |
100 | (void)( \ |
101 | x &= ffff, x ? \ |
102 | ( y &= ffff, y ? \ |
103 | ((y = x * y), x = y & ffff, y = y >> 16, x < y ? \ |
104 | (x = x - y + 1) : (x = x - y)) : \ |
105 | (x = 1 - x)) : \ |
106 | (x = 1 - y) \ |
107 | ) |
108 | |
109 | /*----- Key unpacking functions -------------------------------------------*/ |
110 | |
111 | /* --- @idea_ekeys@ --- * |
112 | * |
113 | * Arguments: @idea_key *k@ = the expanded key buffer |
114 | * @const unsigned char *key@ = the user's key encryption key |
115 | * |
116 | * Returns: --- |
117 | * |
118 | * Use: Unpacks an encryption key. |
119 | */ |
120 | |
121 | void idea_ekeys(idea_key *k, const unsigned char *key) |
122 | { |
123 | /* --- Convince compiler to do this properly --- */ |
124 | |
125 | register const int ffff = 0xFFFF; |
126 | |
127 | uint_32 ka, kb, kc, kd; |
128 | int count; |
129 | int *p = k->k; |
130 | |
131 | /* --- Load the 4 words from the block --- * |
132 | * |
133 | * Don't ask. |
134 | */ |
135 | |
136 | ka = load32(key + 0); |
137 | kb = load32(key + 4); |
138 | kc = load32(key + 8); |
139 | kd = load32(key + 12); |
140 | |
141 | for (count = 48; count > 0; count -= 8) { |
142 | |
143 | /* --- Unpack halfwords into the block --- */ |
144 | |
145 | *p++ = (ka >> 16) & ffff; |
146 | *p++ = ka & ffff; |
147 | *p++ = (kb >> 16) & ffff; |
148 | *p++ = kb & ffff; |
149 | *p++ = (kc >> 16) & ffff; |
150 | *p++ = kc & ffff; |
151 | *p++ = (kd >> 16) & ffff; |
152 | *p++ = kd & ffff; |
153 | |
154 | /* --- Now rotate the 128-bit key --- */ |
155 | |
156 | { |
157 | uint_32 kx = ka; |
158 | ka = ((ka << 25) | (kb >> 7)) & 0xffffffffu; |
159 | kb = ((kb << 25) | (kc >> 7)) & 0xffffffffu; |
160 | kc = ((kc << 25) | (kd >> 7)) & 0xffffffffu; |
161 | kd = ((kd << 25) | (kx >> 7)) & 0xffffffffu; |
162 | } |
163 | } |
164 | |
165 | /* --- Write the tail-enders over --- */ |
166 | |
167 | *p++ = (ka >> 16) & ffff; |
168 | *p++ = ka & ffff; |
169 | *p++ = (kb >> 16) & ffff; |
170 | *p++ = kb & ffff; |
171 | } |
172 | |
173 | /* --- @idea_invertKey@ --- * |
174 | * |
175 | * Arguments: @const idea_key *in@ = pointer to input expanded key buffer |
176 | * @idea_key *out@ = pointer to output expanded key buffer |
177 | * |
178 | * Returns: --- |
179 | * |
180 | * Use: Computes the inverse (decryption) key given an expanded |
181 | * IDEA encryption key. |
182 | */ |
183 | |
184 | void idea_invertKey(const idea_key *in, idea_key *out) |
185 | { |
186 | int i; |
187 | unsigned a, b, c, d, e, f; |
188 | int *ibuf = in->k, *obuf = out->k; |
189 | |
190 | /* --- Deal with identical input and output buffers --- */ |
191 | |
192 | if (in == out) { |
193 | idea_key t; |
194 | memcpy(&t, in, sizeof(t)); |
195 | idea_invertKey(&t, out); |
196 | return; |
197 | } |
198 | |
199 | /* --- Do the real work --- */ |
200 | |
201 | ibuf += IDEA_EXPKEYSIZE; |
202 | for (i = 8; i; i--) { |
203 | ibuf -= 6; |
204 | a = ibuf[0]; |
205 | b = ibuf[1]; |
206 | c = ibuf[2]; |
207 | d = ibuf[3]; |
208 | e = ibuf[4]; |
209 | f = ibuf[5]; |
210 | |
211 | c = idea__inv(c); |
212 | f = idea__inv(f); |
213 | d = 0x10000 - d; |
214 | e = 0x10000 - e; |
215 | |
216 | if (i < 8) |
217 | d ^= e, e ^= d, d ^= e; |
218 | |
219 | obuf[0] = c; |
220 | obuf[1] = d; |
221 | obuf[2] = e; |
222 | obuf[3] = f; |
223 | obuf[4] = a; |
224 | obuf[5] = b; |
225 | obuf += 6; |
226 | } |
227 | |
228 | /* --- Deal with the tail-enders --- */ |
229 | |
230 | ibuf -= 4; |
231 | c = ibuf[0]; |
232 | d = ibuf[1]; |
233 | e = ibuf[2]; |
234 | f = ibuf[3]; |
235 | |
236 | c = idea__inv(c); |
237 | f = idea__inv(f); |
238 | d = 0x10000 - d; |
239 | e = 0x10000 - e; |
240 | |
241 | obuf[0] = c; |
242 | obuf[1] = d; |
243 | obuf[2] = e; |
244 | obuf[3] = f; |
245 | } |
246 | |
247 | /* --- @idea_dkeys@ --- * |
248 | * |
249 | * Arguments: @idea_key *k@ = the expanded key buffer |
250 | * @const unsigned char *key@ = the user's key encryption key |
251 | * |
252 | * Returns: --- |
253 | * |
254 | * Use: Unpacks a decryption key. |
255 | */ |
256 | |
257 | void idea_dkeys(idea_key *k, const unsigned char *key) |
258 | { |
259 | idea_key t; |
260 | idea_ekeys(&t, key); |
261 | idea_invertKey(&t, k); |
262 | } |
263 | |
264 | /*----- Main IDEA cipher --------------------------------------------------*/ |
265 | |
266 | /* --- @idea_encrypt@ --- * |
267 | * |
268 | * Arguments: @const idea_key *k@ = key to use |
269 | * @const void *src@ = block to encrypt |
270 | * @void *dest@ = where to store the result |
271 | * |
272 | * Returns: --- |
273 | * |
274 | * Use: Encrypts (or decrypts) a block, using the IDEA cryptosystem. |
275 | * Since the decryption operation is the same as encryption |
276 | * except that a different key buffer is used, this is all we |
277 | * need to complete the simple bits. |
278 | * |
279 | * For people following this at home: I've been very sloppy |
280 | * about chopping off excess bits from the ints here. Most of |
281 | * the time it doesn't matter, and when it does, in the |
282 | * multiplication stage, the macro does this for us. |
283 | * |
284 | * Our @register const int ffff@ makes another appearance. This |
285 | * might suggest to compilers that having this constant |
286 | * available would be beneficial. |
287 | * |
288 | * Registers are in short supply here. So is legibility. |
289 | */ |
290 | |
291 | #if defined(TEST_RIG) && defined(DUMPROUNDS) |
292 | # define _dump(a,b,c,d) \ |
293 | printf(" %5lu %5lu %5lu %5lu\n", \ |
294 | a & ffff, b & ffff, c & ffff, d & ffff) |
295 | #else |
296 | # define _dump(a,b,c,d) ((void)0) |
297 | #endif |
298 | |
299 | #define _round(a, b, c, d) do { \ |
300 | _dump(a, b, c, d); \ |
301 | u = kp[0]; v = kp[1]; w = kp[2]; x = kp[3]; y = kp[4]; z = kp[5]; \ |
302 | kp += 6; \ |
303 | _mul(a, u); b += v; c += w; _mul(d, x); \ |
304 | u = a ^ c; v = b ^ d; _mul(u, y); v += u; _mul(v, z); u += v; \ |
305 | a ^= v; b ^= u; c ^= v; d ^= u; \ |
306 | _dump(a, b, c, d); \ |
307 | } while (0) \ |
308 | |
309 | void idea_encrypt(const idea_key *k, const void *src, void *dest) |
310 | { |
311 | register const int ffff = 0xFFFF; |
312 | const unsigned char *usrc = src; |
313 | unsigned char *udest = dest; |
314 | int *kp = k->k; |
315 | |
316 | uint_32 a, b, c, d; |
317 | uint_32 u, v, w, x, y, z; |
318 | |
319 | /* --- Unpack next block into registers --- */ |
320 | |
321 | a = (usrc[0] << 8) | usrc[1]; |
322 | b = (usrc[2] << 8) | usrc[3]; |
323 | c = (usrc[4] << 8) | usrc[5]; |
324 | d = (usrc[6] << 8) | usrc[7]; |
325 | |
326 | /* --- Now run the block through the eight rounds --- * |
327 | * |
328 | * Notice how the arguments swap around so as I don't have to move the |
329 | * values about. |
330 | */ |
331 | |
332 | _round(a, b, c, d); |
333 | _round(a, c, b, d); |
334 | _round(a, b, c, d); |
335 | _round(a, c, b, d); |
336 | |
337 | _round(a, b, c, d); |
338 | _round(a, c, b, d); |
339 | _round(a, b, c, d); |
340 | _round(a, c, b, d); |
341 | |
342 | /* --- Do the output transformation --- */ |
343 | |
344 | u = kp[0]; |
345 | v = kp[1]; |
346 | w = kp[2]; |
347 | x = kp[3]; |
348 | _mul(a, u); |
349 | b += w; |
350 | c += v; |
351 | _mul(d, x); |
352 | |
353 | /* --- Repack and store the block --- */ |
354 | |
355 | udest[0] = (a >> 8) & 0xFF; udest[1] = a & 0xFF; |
356 | udest[2] = (c >> 8) & 0xFF; udest[3] = c & 0xFF; |
357 | udest[4] = (b >> 8) & 0xFF; udest[5] = b & 0xFF; |
358 | udest[6] = (d >> 8) & 0xFF; udest[7] = d & 0xFF; |
359 | } |
360 | |
361 | /*----- Debugging driver --------------------------------------------------*/ |
362 | |
363 | #ifdef TEST_RIG |
364 | |
365 | #define TESTENCRYPTION |
366 | |
367 | void dumpbuf(int *k) |
368 | { |
369 | int i; |
370 | printf("Round "); |
371 | for (i = 1; i <= 6; i++) |
372 | printf("%5i ", i); |
373 | for (i = 0; i < 52; i++) { |
374 | if (i % 6 == 0) |
375 | printf("\n %i ", i / 6 + 1); |
376 | printf("%5i ", *k++); |
377 | } |
378 | printf("\n\n"); |
379 | } |
380 | |
381 | void dumpblk(char *bb) |
382 | { |
383 | unsigned char *b = (unsigned char *)bb; |
384 | printf("++ %5u %5u %5u %5u\n", |
385 | (b[0]<<8)|b[1], |
386 | (b[2]<<8)|b[3], |
387 | (b[4]<<8)|b[5], |
388 | (b[6]<<8)|b[7]); |
389 | } |
390 | |
391 | int main(void) |
392 | { |
393 | |
394 | #ifdef TESTMULTIPLY |
395 | { |
396 | unsigned int i, j; |
397 | char buf[256]; |
398 | int ffff = 0xFFFF; |
399 | for (;;) { |
400 | gets(buf); |
401 | if (!buf[0]) |
402 | break; |
403 | sscanf(buf, "%u%u", &i, &j); |
404 | _mul(i, j); |
405 | printf("%u\n", i); |
406 | } |
407 | } |
408 | #endif |
409 | |
410 | #ifdef TESTENCRYPTION |
411 | { |
412 | int i; |
413 | int f; |
414 | |
415 | unsigned char k[] = { 0, 1, 0, 2, 0, 3, 0, 4, 0, 5, 0, 6, 0, 7, 0, 8 }; |
416 | idea_key e, d; |
417 | unsigned char b[] = { 0, 0, 0, 1, 0, 2, 0, 3 }; |
418 | |
419 | static idea_key correct_e = { { |
420 | 1, 2, 3, 4, 5, 6, |
421 | 7, 8, 1024, 1536, 2048, 2560, |
422 | 3072, 3584, 4096, 512, 16, 20, |
423 | 24, 28, 32, 4, 8, 12, |
424 | 10240, 12288, 14336, 16384, 2048, 4096, |
425 | 6144, 8192, 112, 128, 16, 32, |
426 | 48, 64, 80, 96, 0, 8192, |
427 | 16384, 24576, 32768, 40960, 49152, 57345, |
428 | 128, 192, 256, 320 |
429 | } }; |
430 | |
431 | static idea_key correct_d = { { |
432 | 65025, 65344, 65280, 26010, 49152, 57345, |
433 | 65533, 32768, 40960, 52428, 0, 8192, |
434 | 42326, 65456, 65472, 21163, 16, 32, |
435 | 21835, 65424, 57344, 65025, 2048, 4096, |
436 | 13101, 51200, 53248, 65533, 8, 12, |
437 | 19115, 65504, 65508, 49153, 16, 20, |
438 | 43670, 61440, 61952, 65409, 2048, 2560, |
439 | 18725, 64512, 65528, 21803, 5, 6, |
440 | 1, 65534, 65533, 49153 |
441 | } }; |
442 | |
443 | static unsigned char correct_encrypt[] = { |
444 | 4603 / 256, 4603 % 256, |
445 | 60715 / 256, 60715 % 256, |
446 | 408 / 256, 408 % 256, |
447 | 28133 / 256, 28133 % 256 |
448 | }; |
449 | |
450 | static unsigned char correct_decrypt[] = { |
451 | 0, 0, 0, 1, 0, 2, 0, 3 |
452 | }; |
453 | |
454 | idea_ekeys(&e, k); |
455 | dumpbuf(e.k); |
456 | |
457 | f = 1; |
458 | for (i = 0; i < IDEA_EXPKEYSIZE; i++) { |
459 | if (e.k[i] != correct_e.k[i]) { |
460 | f = 0; |
461 | printf("!!! bad encryption key values!\n\n"); |
462 | } |
463 | } |
464 | if (f) |
465 | printf("*** expanded encryption key correct\n\n"); |
466 | |
467 | idea_dkeys(&d, k); |
468 | dumpbuf(d.k); |
469 | |
470 | f = 1; |
471 | for (i = 0; i < IDEA_EXPKEYSIZE; i++) { |
472 | if (d.k[i] != correct_d.k[i]) { |
473 | f = 0; |
474 | printf("!!! bad decryption key values!\n\n"); |
475 | } |
476 | } |
477 | if (f) |
478 | printf("*** expanded decryption key correct\n\n"); |
479 | |
480 | idea_encrypt(&e, b, b); |
481 | dumpblk(b); |
482 | if (memcmp(b, correct_encrypt, 8) == 0) |
483 | printf("*** correct encipherment\n\n"); |
484 | else |
485 | printf("!!! bad encipherment\n\n"); |
486 | |
487 | idea_encrypt(&d, b, b); |
488 | dumpblk(b); |
489 | if (memcmp(b, correct_decrypt, 8) == 0) |
490 | printf("*** correct decipherment\n"); |
491 | else |
492 | printf("!!! bad decipherment\n"); |
493 | } |
494 | #endif |
495 | |
496 | return (0); |
497 | } |
498 | |
499 | #endif |
500 | |
501 | /*----- That's all, folks -------------------------------------------------*/ |